Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 995 · 40 questions

What you do (Heat shows the secret): 1. Dip a cotton bud in lemon juice and write a secret message on white paper. 2. Let the paper dry completely — the writing disappears. 3. An adult irons the paper on a low setting while you watch from a safe distance. 4. Read the brown message and wash your hands.

1. 1.🔮 Predict: the adult irons for only one second. What happens? (a) writing turns green (b) the paper floats (c) writing stays faint (d) it gets darker
2. 2.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “how dark the writing is”? (a) we keep it the same (b) we change it (c) we measure it
3. 3.🛟 Who should use the hot iron in the secret message experiment? (a) any child (b) whoever is fastest (c) the youngest child (d) only an adult
4. 4.🔍 Which is the odd one out? (a) dipping the cotton bud (b) writing the message (c) reading the message (d) ironing the paper
5. 5.🔍 Which is the odd one out? (a) cutting the lemon (b) letting the paper dry (c) ironing the paper (d) putting the iron away
6. 6.🔍 Which is the odd one out? (a) plugging in the iron (b) writing the message (c) cutting the lemon (d) ironing the paper
7. 7.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the iron setting is kept the same. (a) True (b) False
8. 8.🧺 Which of these is needed for the secret lemon message? (a) a battery cell (b) a small bowl (c) a balloon (d) a magnet
9. 9.🛟 Lemon juice stings cuts and eyes. What should you do after the experiment? (a) rub your eyes (b) lick your fingers (c) skip washing (d) wash your hands
10. 10.📘 The browning of lemon juice with heat is a ___ change. (a) magnetic (b) musical (c) physical (d) chemical
11. 11.🍋 Secret message: who does this step — ironing the paper? (a) an adult does it (b) a child can do it
12. 12.🍋 Why can’t you see the lemon writing once it dries? (a) the ink is magnetic (b) it turned into air (c) dry juice is see-through (d) the paper ate it
13. 13.🧺 Do we need a battery cell for the secret lemon message? (a) needed (b) not needed
14. 14.🧺 Which of these is not needed for the secret lemon message? (a) a small bowl (b) white paper (c) a magnet (d) a cotton bud
15. 15.🍋 Secret message: who does this step — cutting the lemon? (a) an adult does it (b) a child can do it
16. 16.🧺 Which of these is not needed for the secret lemon message? (a) lemon juice (b) an adult with an iron (c) a small bowl (d) yeast
17. 17.🍋 Which of these steps is a job for an adult? (a) reading the message (b) writing the message (c) dipping the cotton bud (d) plugging in the iron
18. 18.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the same paper is kept the same. (a) False (b) True
19. 19.🧺 Which of these is not needed for the secret lemon message? (a) lemon juice (b) a balloon (c) white paper (d) an adult with an iron
20. 20.True or false: letting the paper dry is a job for an adult. (a) True (b) False
21. 21.🧺 Which of these is needed for the secret lemon message? (a) a mirror (b) an adult with an iron (c) a balloon (d) turmeric powder
22. 22.🍋 Secret message: who does this step — dipping the cotton bud? (a) a child can do it (b) an adult does it
23. 23.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the same cotton bud”? (a) we change it (b) we keep it the same (c) we measure it
24. 24.True or false: a mirror is not needed for the secret lemon message. (a) True (b) False
25. 25.🔍 Which is the odd one out? (a) putting the iron away (b) letting the paper dry (c) dipping the cotton bud (d) reading the message
26. 26.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the same paper”? (a) we change it (b) we keep it the same (c) we measure it
27. 27.🍋 Why does the lemon writing turn brown with heat? (a) the juice scorches first (b) heat adds colour (c) paper turns lemony (d) the iron is brown
28. 28.True or false: yeast is not needed for the secret lemon message. (a) True (b) False
29. 29.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a small bowl (b) a mirror (c) white paper (d) a cotton bud
30. 30.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is what we measure? (a) the same paper (b) the same cotton bud (c) how dark the writing is (d) the iron setting
31. 31.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the kind of juice”? (a) we change it (b) we measure it (c) we keep it the same
32. 32.True or false: dipping the cotton bud is a job for an adult. (a) True (b) False
33. 33.🔮 Can the brown writing go back to being invisible? (a) yes, if cooled (b) no, it stays brown (c) yes, if shaken (d) yes, in the dark
34. 34.🍋 What colour does the lemon writing turn when an adult warms it? (a) brown (b) green (c) white (d) blue
35. 35.🧺 Do we need yeast for the secret lemon message? (a) needed (b) not needed
36. 36.🔮 Predict: you write with plain water instead of lemon juice. What appears after ironing? (a) dark brown words (b) blue words (c) almost nothing (d) a rainbow
37. 37.🧺 Which of these is needed for the secret lemon message? (a) turmeric powder (b) a balloon (c) a battery cell (d) white paper
38. 38.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is the one thing we change? (a) the same cotton bud (b) the kind of juice (c) the iron setting (d) the same paper
39. 39.🍋 Which of these steps is a job for an adult? (a) letting the paper dry (b) dipping the cotton bud (c) reading the message (d) cutting the lemon
40. 40.🔍 Which is the odd one out? (a) reading the message (b) writing the message (c) dipping the cotton bud (d) plugging in the iron

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